Mix soji, powdered spices, yogurt, ginger, green chili, 3 tbsp oil, vegetable, and add water slowly to prepare batter.
Make a thickish batter, adding buttermilk or water accordingly.
Keep aside for 30 minutes.
Now gently mix in soda. Add soda at last right before cooking. Never add soda ahead of time.
Put a med. heavy saucepan or kadai to heat.
Put 3 tbsp. oil in pan, add mustard seeds.
Allow to splutter. When done add curry leaves, sesame seeds.
Pour batter carefully in oil. Spread batter evenly.
Cover and allow to cook on very low.
When the base turns crisp and golden brown, flip over.
Allow other side to become crisp.
Serve hot with green chutney or sauce.
Repeat with remaining batter if you have some batter left. If usually make big handvo in wide pan.
If many are required at a time, use more than one stoves and pans.
Or use the paddu tava.(It is a thick iron griddle with cup depressions like muffin trays.)
Batter can be stored for few hours, add soda when required.